Use of reversed phase HP liquid chromatography to assay conversion of N-acylglycines to primary fatty acid amides by peptidylglycine-alpha-amidating monooxygenase

Surgery-induced gut microbial dysbiosis promotes cognitive impairment via regulation of intestinal function and the metabolite palmitic amide

BACKGROUND

Perioperative neurocognitive disorders (PND) are the most common postoperative complications with few therapeutic options. Gut microbial dysbiosis is associated with neurological diseases; however, the mechanisms by which the microbiota regulates postoperative gastrointestinal and cognitive function are incompletely understood.

METHODS

Behavioral testing, MiSeq 16S rRNA gene sequencing, non-target metabolism, intestinal permeability detection, protein assays, and immunofluorescence staining were employed to discern the impacts of surgery on microbial profiles, intestinal barriers, serum metabolism, and the brain. Interventions in mice included fecal microbiota transplantation, the anti-inflammatory agent dexamethasone, Lactobacillus supplementation, indole propionic acid supplementation, and palmitic amide administration.

RESULTS

Surgery-induced cognitive impairment occurs predominantly in aged mice, and surgery-induced alterations in the microbiota composition profile exacerbate intestinal barrier disruption in aged mice. These adverse effects can be mitigated by transferring microbiota from young donors or by bolstering the intestinal barrier function using dexamethasone, Lactobacillus, or indole propionic acid. Moreover, microbiota composition profiles can be restored by transplanting feces from young mice to aged surgical mice, improving neuropathology and cognitive function, and these effects coincide with increased intestinal permeability. Metabolomic screening identified alterations in metabolites in mouse serum after surgery, especially the increase in palmitic amide. Palmitic amide levels in serum and brain can be decreased by transplanting feces from young mice to aged surgical mice. Oral palmitic amide exacerbates cognitive impairment and neuropathological changes in mice.

CONCLUSIONS

Gut microbial dysbiosis in mice after surgery is a key mechanism leading to cognition dysfunction, which disrupts the intestinal barrier and metabolic abnormalities, resulting in neuroinflammation and dendritic spine loss. Intestinal barrier damage and high level of palmitic amide in old mice may be the cause of high incidence of PND in the elderly. Preoperative microbiota regulation and intestinal barrier restoration may be of therapeutic benefit in preventing PND. Video Abstract.

Common Metabolites in Two Different Hypertensive Mouse Models: A Serum and Urine Metabolome Study

Recent metabolomics studies have identified a wide array of microbial metabolites and metabolite pathways that are significantly altered in hypertension. However, whether these metabolites play an active role in pathogenesis of hypertension or are altered because of this has yet to be determined. In the current study, we hypothesized that metabolite changes common between hypertension models may unify hypertension's pathophysiology with respect to metabolites. We utilized two common mouse models of experimental hypertension: L-arginine methyl ester hydrochloride (L-NAME)/high-salt-diet-induced hypertension (LSHTN) and angiotensin II induced hypertension (AHTN). To identify common metabolites that were altered across both models, we performed untargeted global metabolomics analysis in serum and urine and the resulting data were analyzed using MetaboAnalyst software and compared to control mice. A total of 41 serum metabolites were identified as being significantly altered in any hypertensive model compared to the controls. Of these compounds, 14 were commonly changed in both hypertensive groups, with 4 significantly increased and 10 significantly decreased. In the urine, six metabolites were significantly altered in any hypertensive group with respect to the control; however, none of them were common between the hypertensive groups. These findings demonstrate that a modest, but potentially important, number of serum metabolites are commonly altered between experimental hypertension models. Further studies of the newly identified metabolites from this untargeted metabolomics analysis may lead to a greater understanding of the association between gut dysbiosis and hypertension.

Development of a Microfluidic Platform for Trace Lipid Analysis

The inherent trace quantity of primary fatty acid amides found in biological systems presents challenges for analytical analysis and quantitation, requiring a highly sensitive detection system. The use of microfluidics provides a green sample preparation and analysis technique through small-volume fluidic flow through micron-sized channels embedded in a polydimethylsiloxane (PDMS) device. Microfluidics provides the potential of having a micro total analysis system where chromatographic separation, fluorescent tagging reactions, and detection are accomplished with no added sample handling. This study describes the development and the optimization of a microfluidic-laser induced fluorescence (LIF) analysis and detection system that can be used for the detection of ultra-trace levels of fluorescently tagged primary fatty acid amines. A PDMS microfluidic device was designed and fabricated to incorporate droplet-based flow. Droplet microfluidics have enabled on-chip fluorescent tagging reactions to be performed quickly and efficiently, with no additional sample handling. An optimized LIF optical detection system provided fluorescently tagged primary fatty acid amine detection at sub-fmol levels (436 amol). The use of this LIF detection provides unparalleled sensitivity, with detection limits several orders of magnitude lower than currently employed LC-MS techniques, and might be easily adapted for use as a complementary quantification platform for parallel MS-based omics studies.

Unraveling the metabolic response of Brassica oleracea exposed to Xanthomonas campestris pv. campestris

BACKGROUND

Brassica crops together with cereals represent the basis of world supplies. Due to their importance, the production losses caused by Xanthomonas campestris pv. campestris (Xcc) infection represent a high economic impact. Understanding molecular and biochemical mechanisms of plants is essential to develop resistant crops with durable protection against diseases. In this regard, metabolomics has emerged as a valuable technology to provide an overview of the biological status of a plant exposed to a disease. This study investigated the dynamic changes in the metabolic profile of Brassica oleracea plants during an Xcc infection from leaves collected at five different days post infection using a mass spectrometry approach.

RESULTS

Results showed that Xcc infection causes dynamic changes in the metabolome of B. oleracea. Moreover, induction/repression pattern of the metabolites implicated in the response follows a complex dynamics during infection progression, indicating a complex temporal response. Specific metabolic pathways such as alkaloids, coumarins or sphingolipids are postulated as promising key role candidates in the infection response.

CONCLUSION

This work tries to decipher the changes produced on Brassica crops metabolome under Xcc infection and represents a step forward in the understanding of B. oleracea-Xcc interaction. © 2018 Society of Chemical Industry.

Tissue storage affects lipidome profiling in comparison to in vivo microsampling approach

Low-invasive in vivo solid-phase microextraction (SPME) was used to investigate the lipid profiles of muscle tissue of living fish. Briefly, mixed mode SPME fibers were inserted into the muscle for 20 min extraction, and then the fibers were desorbed in an optimal mixture of solvents. The obtained lipid profile was then compared and contrasted to that obtained with employment of ex vivo SPME and solid-liquid extraction (SLE) from fish muscle tissue belonging to the same group of fish, following a one-year storage period. Ex vivo SPME analysis of stored muscle samples revealed 10-fold decrease in the number of detected molecular features in comparison to in vivo study. Moreover, in vivo microsampling enabled the identification of different classes of bioactive lipids, including fatty acyls, not present in the lipid profile obtained through ex vivo SPME and SLE, suggesting the alterations occurring in the unbound lipid fraction of the system under study during the storage and also indicating the advantage of the in vivo extraction approach.

Electrospray ionization and collision induced dissociation mass spectrometry of primary fatty acid amides

Primary fatty acid amides are a group of bioactive lipids that have been linked with a variety of biological processes such as sleep regulation and modulation of monoaminergic systems. As novel forms of these molecules continue to be discovered, more emphasis will be placed on selective, trace detection. Currently, there is no published experimental determination of collision induced dissociation of PFAMs. A select group of PFAM standards, 12 to 22 length carbon chains, were directly infused into an electrospray ionization source Quadrupole Time of Flight Mass Spectrometer. All standards were monitored in positive mode using the [M + H](+) peak. Mass Hunter Qualitative Analysis software was used to calculate empirical formulas of the product ions. All PFAMs showed losses of 14 m/z indicative of an acyl chain, while the monounsaturated group displayed neutral losses corresponding to H(2)O and NH(3). The resulting spectra were used to propose fragmentation mechanisms. Isotopically labeled PFAMs were used to validate the proposed mechanisms. Patterns of saturated versus unsaturated standards were distinctive, allowing for simple differentiation. This determination will allow for fast, qualitative identification of PFAMs. Additionally, it will provide a method development tool for selection of unique product ions when analyzed in multiple reaction monitoring mode.

Quantification of primary fatty acid amides in commercial tallow and tallow fatty acid methyl esters by HPLC-APCI-MS

Primary fatty acid amides are a group of biologically highly active compounds which were already identified in nature. Here, these substances were determined in tallow and tallow fatty acid methyl esters for the first time. As tallow is growing in importance as an oleochemical feedstock for the soap manufacturing, the surfactant as well as the biodiesel industry, the amounts of primary fatty acid amides have to be considered. As these compounds are insoluble in tallow as well as in the corresponding product e.g. tallow fatty acid methyl esters, filter plugging can occur. For the quantification in these matrices a purification step and a LC-APCI-MS method were developed. Although quantification of these compounds can be performed by GC-MS, the presented approach omitted any derivatization and increased the sensitivity by two orders of magnitude. Internal standard calibration using heptadecanoic acid amide and validation of the method yielded a limit of detection of 18.5 fmol and recoveries for the tallow and fatty acid methyl ester matrices of 93% and 95%, respectively. A group of commercially available samples were investigated for their content of fatty acid amides resulting in an amount of up to 0.54%m/m (g per 100 g) in tallow and up to 0.16%m/m (g per 100 g) in fatty acid methyl esters.